In the electron transport chain, electrons from FADH2 are eventually used to reduce O2 into H2O. Experimentally, the proton motive force created by this process will generate 2 ATP molecules from ADP and Pi, using ATP synthase. From the information provided below, calculate the efficiency for the system
Efficiency = Energy stored/ Energy produced
FAD + 2 H + 2e = FADH2 Eo’ = - 0.22
.5 O2 + 2 H + 2e = H2O Eo’ = 0.82
ATP = ADP + Pi ΔGo’ = 30.5 kJ/mol
To calculate the efficiency of the system, we need to determine the energy stored and the energy produced.
Energy produced:
To calculate the energy produced, we need to consider the reduction of FAD to FADH2 and the reduction of O2 to H2O. The energy change for each reaction can be calculated using the Nernst equation:
∆G = -nF∆Eo'
Where:
∆G is the change in free energy
n is the number of moles of electrons transferred
F is Faraday's constant (96,485 C/mol)
∆Eo' is the standard reduction potential
For the reduction of FAD to FADH2:
∆G for the reaction = -2 * F * ∆Eo'
∆G = -2 * 96,485 * (-0.22) = 42,426 J/mol
For the reduction of O2 to H2O:
∆G for the reaction = -4 * F * ∆Eo'
∆G = -4 * 96,485 * (0.82) = -317,571 J/mol
Total energy produced = ∆G FADH2 + ∆G H2O = 42,426 + (-317,571) = -275,145 J/mol
Energy stored:
To calculate the energy stored, we need to determine the energy released during the formation of ATP from ADP and Pi. The energy change (∆G) for this reaction is given as 30.5 kJ/mol.
Total energy stored = ∆G ATP = 30.5 kJ/mol = 30,500 J/mol
Efficiency:
To calculate efficiency, we divide the energy stored by the energy produced:
Efficiency = Energy stored / Energy produced
Efficiency = 30,500 / -275,145
Note that energy produced is negative, as it represents the energy released during the reactions.
The efficiency for the system is the absolute value of the ratio of energy stored to energy produced:
Efficiency = |30,500 / -275,145| ≈ 0.111 or 11.1%
Therefore, the efficiency of the system is approximately 11.1%.